1. Field of the Invention
The present invention relates to a signal drive apparatus in which a plurality of buffer circuits are arranged in parallel and the buffer circuits are switched to output a signal and an optical pickup apparatus using the signal drive apparatus. In particular, the buffer circuits having a plurality of light detecting circuits are switched to disconnect the buffer circuit for optical detection which is not in operation, and an optical detection signal is supplied to a following signal-processing circuit via a flexible substrate (or cable).
2. Description of the Related Art
FIG. 1 shows a conventional optical pickup apparatus 200 which has external changeover switches, switches the changeover switches, selects signals detected by a plurality of PD's (photo-detecting diode), and transfers the thus selected data by means of one flexible substrate (also referred to as a cable). This optical pickup apparatus 200 is constituted by an OEIC (Optical Electoro IC; photoelectric conversion integrated circuit) 201 for BD (Blu-ray laser diode), an OEIC 202 for DVD (Digital Versatile Disc)/CD (Compact Disc), a switch 203 for switching between outputs from these, one flexible substrate 204, and a signal processing IC.
During recording and reproduction by means of a Blu ray LD (Blu ray laser diode), a laser diode for DVD/CD stops emitting light or, alternatively, is operated to transfer any one of the signals (data) of the OEIC 201 for BD and the OEIC 202 for DVD/CD by means of one flexible substrate. Thus, the changeover switch 203 is provided for choosing the signals alternatively and transmitting the signal from any one of the OEIC's.
When transferring the output data to a signal-processing IC 205 from the OEIC 201 for BD, the changeover switch 203 is switched to the OEIC 201 side for BD, and the output data (signal) from the OEIC 201 for BD is outputted to the flexible substrate 204. At the same time, a drive circuit provided at a following stage of the OEIC 202 for DVD/CD is in operation. However, since it is switched with the changeover switch 203, the output of OEIC for DVD/CD does not adversely influence the operation of the drive circuit in an output stage of the OEIC 201 for BD.
Conversely, when transferring the output signal from the OEIC 202 for DVD/CD via the flexible substrate 204 to a signal-processing (IC) circuit 205, the changeover switch 203 is switched to the OEIC 202 side for DVD/CD. Then, the signal outputted from the OEIC for DVD/CD is transferred to the signal-processing IC 205 through the flexible substrate 204.
At this time, since the drive circuit of the output stage of the OEIC 201 for BD is switched with the changeover switch 203, it does not affect the output of the drive circuit of the OEIC for DVD/CD.
Although one flexible substrate is arranged, using the switch leads to a disadvantage that a space is needed and costs are high.
Another conventional optical pickup apparatus 250 is shown in FIG. 2. This optical pickup apparatus 250 is arranged to use two flexible substrates. An output signal of an OEIC 251 for BD is outputted to a signal-processing IC 255 via a flexible substrate 253. Further, an output signal of an OEIC 252 for DVD/CD is outputted to a signal-processing IC 255 via a flexible substrate 254 which is further provided.
An output terminal of the OEIC 251 for BD is connected with the signal-processing IC 255 via the flexible substrate 253. Further, an output terminal of the OEIC 252 for DVD/CD is connected to the signal-processing IC 255 via the flexible substrate 254. Therefore, it is necessary for the signal-processing IC 255 side to switch between the signals by means of a control signal, whereby either the signal is supplied from the OEIC 251 for BD or the signal is supplied from the OEIC 252 for DVD/CDE.
Furthermore, the conventional optical pickup apparatus 250 requires at least two flexible substrates. Thus, there is a disadvantage that signal interference takes place between the flexible substrates, a noise may be introduced, etc., and a transferred signal may deteriorate, which also leads to a malfunction.
Still further, since two or more (plural) flexible substrates are needed, there is a disadvantage that a space is needed, it is difficult to miniaturize the apparatus, and the cost increases with an increasing number of flexible substrates.